Semiconductor structure and the manufacturing method thereof

ABSTRACT

The present invention provides a semiconductor structure for forming a CMOS image sensor. The semiconductor structure includes at least a photodiode formed in the substrate for collecting photoelectrons, and the photodiode has a pinning layer, a first doped region and a second doped region in order from top to bottom in a height direction of the substrate. The semiconductor structure further includes a third doped region located in the substrate corresponding to a laterally extending region of the second doped region. The first doped region has an ion doping concentration greater than the ion doping concentration of the second doped region, the ion doping concentration of the second doped region is greater than the ion doping concentration of the third doped region, and the third doped region is in contact with the second doped region after diffusion. The present invention also provides a method of manufacturing the above-described semiconductor structure.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority to Chinese Patent ApplicationNo. 201910265516.1, filed Apr. 3, 2019, the entire contents of which isincorporated herein for all purposes by this reference.

TECHNICAL FIELD

The present invention relates to the field of semiconductor devices andtheir fabrication, and more particularly to CMOS image sensor structuresand their fabrication.

BACKGROUND ART

With the development of the automotive industry, the Internet of Thingsand monitoring equipment, the consumption of image sensors has graduallyincreased. Only when the accurate patterns full of details can beobtained through the image sensor with good performance, the subsequentimplementation of various functions is possible. In particular, thedemand for near-infrared light for in-vehicle recorders and monitoringequipment has recently increased. The image sensor equipped withnear-infrared light technology which enables the image sensor to captureimages under dark conditions, and the captured image can contain moredetails of the object in dark light, especially suitable for the devicethat captures the image in dark light conditions.

The photoreceptor of the current CMOS image sensor is mainly classifiedinto a front side illumination (FSI) and a backside illumination (BSI)according to the positional relationship between the light incidentdirection and the substrate and the metal connection layer. For theacquisition of near-infrared light (wavelength greater than 760 nm), thecommonly used FSI structures and manufacturing methods are mainlydivided into two types: one is to use ultra-high energy implantation onan N-type substrate to achieve ultra-deep boron (B) implantation (energyis greater than 4 MeV) and phosphorus (P) implantation (energy greaterthan 7 MeV). These pinned diodes can achieve a depth of 6 um and havegood electrical isolation, using a strong barrier to isolate illuminatedpixels and adjacent pixels. The other is to increase a thickness of thehigh-resistance P-type substrate, in this method, the efficiency ofcollection depends on the initial thickness of the wafer and the thermalbudget experienced by the process. High-resistance substrates areprimarily used to reduce interference from adjacent pixels caused bypinning diode induced potential.

As the pixel unit is reduced, in order to increase the amount of lightentering, the industry has tried to adopt a BSI structure. For the BSIstructure, since the silicon wafer needs to be thinned to increase thelight transmission, and the absorption of visible red light isconsidered, the thickness of the silicon wafer is generally defined as2.4 um (the intensity of the red light is the original 1/e). For theBSI-sensing structure, Sony has proposed a pyramid-type surface using asilicon crystal plane to increase the near-infrared quantum efficiency(QE) structure, and combined with deep isolation, can effectivelyimprove the quantum efficiency of near-infrared light without increasingdark current. Howe's Nighthawk Nyxel technology combines thick siliconpixel architecture with Deep Trench Isolation (DTI) to improve quantumefficiency. By carefully managing the surface texture of the wafer tomaintain the modulation transfer function, it does not affect the darkcurrent of the sensor. Achieve clearer imaging with the samenear-infrared light volume, or cover farther areas, or reduce the needfor LED lights and reduce total power consumption.

The existing near-infrared light design focuses on the requirements forcontinuous image processing (video surveillance, driving recorders,autopilot cameras), and less consideration for combining static highspeed. For high-speed global shutter camera (Free Join SHUTTER), itneeds to completely occlude the storage node of the storage transistorto achieve accurate signal transfer. In the prior art, metal tungsten isused for occlusion, therefore photoreceptor structure using an FSIstructure.

However, for near-infrared light, it is difficult to achieve the effectof not affecting the storage node. This is because the wavelength of thenear-infrared light is large, and the silicon substrate thickened toenhance the optical path causes the regions to be affected by light togenerate photoelectrons.

Please refer to FIG. 1 and FIG. 2 . FIG. 1 shows the variation of thelight intensity of four different wavelengths with the penetrationdepth. As can be seen from FIG. 1 , when penetrating into the siliconsubstrate, the penetration depth of blue light (the wavelength of the450 nm curve) while the intensity attenuates to 1/e is about 0.42 um,the green light (the wavelength of the 550 nm curve) is 1.40 um, and thered light (the wavelength of the spectrum is 600 nm) is 2.42 um, whilenear-infrared light (wavelength 850 nm in the figure) has a deepabsorption range due to wavelength. Referring to FIG. 2 , FIG. 2 showsthe relationship between the parasitic light response of the storagenode and the wavelength. It can be seen that the larger the wavelength,the stronger the corresponding parasitic effect, and the effect of theparasitic light becomes more serious for the near-infrared opticaldevice.

At the same time, due to the need to completely block the storage nodeby using metal, the effective area of the photodiode (PD) region islowered, and the overall photoresponse is lowered, resulting in adecrease in device performance.

Therefore, there is a need for a semiconductor structure in which a CMOSimage sensor can overcome the above-mentioned problem of parasitic lightcaused by a long wavelength of near-infrared light and the problem thatthe overall light response of the device is lowered.

SUMMARY OF THE INVENTION

A brief summary on one or more aspects is given below to provide thebasic understanding for these aspects. This summary is not an exhaustiveoverview of all the contemplated aspects and is neither intended toindicate critical or decisive elements of all aspects nor to attempt todefine the scope of any or all aspects. Its sole purpose is to presentsome concepts of one or more aspects in a simplified form as a prefacefor a more detailed description presented later.

In order to solve the above problems, a semiconductor structure capableof enhancing near-infrared light processing capability is provided, andthe present invention provides a semiconductor structure for forming aCMOS image sensor. The semiconductor structure comprising at least aphotodiode formed in a substrate (100) for collecting photoelectrons,wherein the photodiode has a pinning layer (210), a first doped region(220) and a second doped region (230) in order from top to bottom in aheight direction of the substrate; and

the semiconductor structure further includes a third doped region (300),wherein the third doped region (300) is located in the substrate (100)corresponding to a laterally extending region of the second doped region(230); wherein

the ion doping concentration of the first doped region (220) is greaterthan the ion doping concentration of the second doped region (230), andthe ion doping concentration of the second doped region (230) is greaterthan the ion doping concentration of the third doped region (300), thethird doped region (300) is in contact with the second doped region(230) after diffusion.

In an embodiment of the semiconductor structure, optionally, the firstdoped region (220), the second doped region (230) and the third dopedregion (300) are all of a first ion doping type.

In an embodiment of the semiconductor structure, optionally, thesubstrate (100) and the pinning layer (210) are both of a second iondoping type, and the second ion doping type is different from the firstion doping type, the ion doping concentration of the pinned layer (210)is greater than the ion doping concentration of the substrate (100).

In an embodiment of the semiconductor structure, optionally, thesemiconductor structure further comprises a storage node formed in thesubstrate (100), having a pinning layer (410) and an ion doped region(420) in order from top to bottom in the height direction of thesubstrate, the third doped region (300) is formed under the storagenode, and the third doped region (300) and the ion doped region (420) ofthe storage node are isolated from each other.

In an embodiment of the semiconductor structure, optionally, the thirddoped region (300) and the ion doped region (420) of the storage nodeare both of a first ion doping type, and the ion doping concentration ofthe ion doped region (420) of the storage node is greater than the iondoping concentration of the third doped region (300).

In an embodiment of the semiconductor structure, optionally, thesemiconductor structure further comprises a fourth doped region (500),the third doped region (300) is isolated from the ion doped region (420)of the storage node by the fourth doped region (500).

In an embodiment of the semiconductor structure, optionally, thesubstrate (100) and the fourth doped region (500) are both of a secondion doping type, the second ion doping type is different from the firstion doping type, the ion doping concentration of the fourth doped region(500) is greater than the ion doping concentration of the substrate(100).

In an embodiment of the semiconductor structure, optionally, the fourthdoped region (500) further comprises an extension extending laterallytoward the photodiode, and

the extension further extends upward in the height direction of thesubstrate.

The present invention also provides a manufacturing method ofmanufacturing a semiconductor structure for forming a CMOS image sensor,the manufacturing method comprising:

providing a substrate (100);

forming a second doped region (230), a first doped region (220) and apinning layer (210) sequentially from bottom to top in a heightdirection of the substrate in the substrate (100) to form a photodiodeof the CMOS image sensor; and

forming a third doped region (300) in the substrate (100) correspondingto a laterally extending region of the second doped region (230),wherein

the ion doping concentration of the first doped region (220) is greaterthan the ion doping concentration of the second doped region (230), andthe ion doping concentration of the second doped region (230) is greaterthan the ion doping concentration of the third doped region (300) suchthat the formed third doped region (300) is in contact with the seconddoped region (230) after diffusion.

In an embodiment of the above manufacturing method, optionally, a firsttype of ion doping is performed to form the first doped region (220),the second doped region (230) and the third doped region (300).

In an embodiment of the above manufacturing method, optionally, a secondtype of ion doping is performed to provide the substrate (100) and toform the pinning layer (210), wherein the second ion doping type isdifferent from the first ion doping type; and

the ion doping concentration of the pinned layer (210) is greater thanthe ion doping concentration of the substrate (100).

In an embodiment of the above manufacturing method, optionally, themanufacturing method further comprises:

forming an ion doped region (420) and a pinning layer (410) in orderfrom bottom to top in the substrate (100) in the substrate heightdirection to form a storage node of the CMOS image sensor; and

the storage node is formed over the third doped region (300), and thethird doped region (300) is isolated from the ion doped region (420) ofthe storage node.

In an embodiment of the above manufacturing method, optionally, thefirst type of ion doping is performed to form the third doped region(300) and the ion doped region (420) of the storage node; and

the ion doping concentration of the ion doped region (420) of thestorage node is greater than the ion doping concentration of the thirddoped region (300).

In an embodiment of the above manufacturing method, optionally, themanufacturing method further comprises:

forming a fourth doped region (500) between the third doped region (300)and the ion doped region (420) of the storage node, the third dopedregion (300) is isolated from the ion doped region (420) of the storagenode by the fourth doped region (500).

In an embodiment of the above manufacturing method, optionally, a secondtype of ion doping is performed to provide the substrate (100) and toform the fourth doped region (500), wherein the second ion doping typeis different from the first ion doping type; and

the ion doping concentration of the fourth doped region (500) is greaterthan the ion doping concentration of the substrate (100).

In an embodiment of the above manufacturing method, optionally, formingthe fourth doped region (500) further comprises forming an extensionextending laterally toward the photodiode, and

forming the extension further includes extending the extension upward ina height direction of the substrate.

The semiconductor structure provided according to the present inventionadditionally adds an electron collecting region in the substrate, canachieve more absorption of near-infrared light, can enhance the abilityof the image sensor to process near-infrared light, and improve theaccuracy of the global electronic shutter. The manufacturing method ofthe above semiconductor structure provided by the invention is simple inprocess, compatible with the existing process flow, and does notadditionally increase the manufacturing cost.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the relationship between the light intensity of differentwavelengths of light and the penetration depth.

FIG. 2 shows the relationship between the parasitic light response andthe wavelength of light.

FIG. 3 shows a schematic structural view of a CMOS image sensor.

FIG. 4 is a schematic diagram showing a first embodiment of a CMOS imagesensor structure provided by the present invention.

FIG. 5 is a schematic diagram showing a second embodiment of a CMOSimage sensor structure provided by the present invention.

FIG. 6 is a schematic diagram showing a third embodiment of a CMOS imagesensor structure provided by the present invention.

FIG. 7A shows the energy potential diagram along the AA′ direction inthe third embodiment shown in FIG. 6 .

FIG. 7B shows the energy potential diagram along the BB′ direction inthe third embodiment shown in FIG. 6 .

FIG. 8 is a flow chart showing the manufacturing method provided by thepresent invention.

REFERENCE SIGNS

100 substrate 210 pinning layer 220 first doped region 230 second dopedregion 300 third doped region 410 pinning layer 420 ion doped region 500fourth doped region 510 extending portion TX1 first transfer transistorTX2 second transfer transistor GS global shutter RS selection transistorRST reset transistor FD floating diffusion point STI shallow trenchisolation

DETAILED DESCRIPTION OF EMBODIMENTS

The present invention relates to a semiconductor device and a method ofmanufacturing the same. More specifically, embodiments of the presentinvention provide a semiconductor structure for forming a CMOS imagesensor that additionally adds an ion doped region in the substrate forcollecting photoelectrons. Other embodiments are also provided.

The following description is presented to enable one of ordinary skillin the art to implement and use the present invention and incorporate itinto the context of a particular application. Various modifications, aswell as various usages in various applications, will be readily apparentto those skilled in the art, and the generic principles defined hereinmay be applicable to a wide range of embodiments. Thus, the presentinvention is not limited to the embodiments presented herein, but rathershould be given its broadest scope consistent with the principles andnovel features disclosed herein.

In the following detailed description, numerous specific details are setforth to provide a more thorough understanding of the present invention.However, it will be apparent to those skilled in the art that thepresent invention may be practiced without limitations from thesespecific details. In other words, well-known structures and devices areshown in a block diagram form and are not shown in detail, so as toavoid obscuring the present invention.

The reader is cautioned as to all files and documents which are filed atthe same time as this specification and which are open for the public toconsult, and the contents of all such files and documents areincorporated herein by reference. Unless directly stated otherwise, allfeatures disclosed in this specification (including any of the appendedclaims, the abstract, and the accompanying drawings) may be replaced byalternative features serving the same, equivalent, or similar purposes.Therefore, unless expressly stated otherwise, each of the featuresdisclosed is only one example of a group of equivalent or similarfeatures.

Note that when used, the flags left, right, front, back, top, bottom,front, back, clockwise, and counter-clockwise are used for conveniencepurposes only and do not imply any specific fixed direction. In fact,they are used to reflect the relative position and/or direction betweenvarious parts of an object.

As used herein, the terms “over . . . “under . . . ”, “between . . . and. . . ”, and “on . . . ” means the relative position of that layerrelative to another layer. Likewise, for example, a layer that isdeposited or placed over or under another layer may be in direct contactwith another layer or there may be one or more intervening layers. Inaddition, a layer that is deposited or placed between layers may be indirect contact with the layers or there may be one or more interveninglayers. In contrast, a first layer “on” a second layer is in contactwith the second layer. In addition, a relative position of a layerrelative to another layer is provided (assuming that film operations ofdeposition, modification, and removal are performed in relative to astarting substrate, without considering the absolute orientation of thesubstrate).

First, please refer to FIG. 3 . FIG. 3 shows a schematic structuraldiagram of a 6T active CMOS image sensor. In this structure, thephotodiode for collecting photoelectrons includes a pinning layer 210, afirst doped region 220, and a second doped region 230, wherein the iondoping concentration of the second doped region 230 is lower than theion doping concentration of the first doped region 220. The operation ofthe structure is as follows: (1) light enters the photodiode, as shownby the solid arrow in the figure, and photoelectrons generated in theprocess are collected by the first doped region 220 and the second dopedregion 230. Since the ion doping concentration of the second dopingregion 230 is lower than the ion doping concentration of the firstdoping region 220, a transfer path in which photoelectrons arelongitudinally transferred from the second doped region 230 to the firstdoped region 220 is formed. The photoelectrons collected by the seconddoped region 230 are then stored in the first doped region 220, and inorder to prevent the ion doped region 420 of the storage node from beingdisturbed by noise, a shading material is usually disposed above thestorage node, such as the metal tungsten shown in FIG. 3 . (2), turningon the first transfer transistor TX1, and transferring the charge of allthe pixel units from the photodiode to the ion doped region 420 of thestorage node, wherein the charge that is desired to be transferred isthe charge stored in the first doped region 220 of the photodiode,rather than other noisy electrons. (3), the first transfer transistorTX1 is turned off, so that photoelectrons exist in the storage node,specifically in the ion doped region 420 of the storage node. (4), theshutter gate GS connected to the photodiode is turned on to transferresidual charge in the photodiode, and at the same time, it can preventany additional photosensitive generated photoelectrons. (5), the chargeis read out in a row from the ion doped region 420 of the storage nodethrough the second transfer transistor TX2 and the floating diffusionpoint FD. The step and the subsequent steps of reading are realized bycontrolling the selection transistor RS and the reset transistor RST,and are not described herein.

In the structure shown in FIG. 3 , if it is used to collectnear-infrared light, as shown by the solid arrow in FIG. 3 , since thewavelength of the near-infrared light is large, usually up to 840 um,950 um, etc., there is a long optical path, and it is easy to enter theadjacent area (as shown by the dotted arrow in the figure). The storagenode only stores photoelectrons from the photodiode and cannot beirradiated by external light, but these free photoelectrons cause theion doped region 420 of the storage node to be affected by the incidentlight when the first transfer transistor TX1 is not yet turned on, whichcausing noise interference. Moreover, these free photoelectrons alsoreduce the photoresponse of the photodiode itself. Therefore, the CMOSimage sensor structure as shown in FIG. 3 is not suitable for the casewhere dark light requires the use of near-infrared light technology.

To solve the above problems, the present invention provides a method ofmanufacturing a semiconductor structure for forming a CMOS image sensor,please refer to FIG. 4 . The semiconductor structure shown in FIG. 4includes a substrate 100, a photodiode formed in the substrate 100, andthe photodiode has a pinning layer 210, a first doped region 220 and asecond doped region 230 in order from the top to the bottom in thesubstrate height direction, wherein the ion doping concentration of thesecond doped region 230 is lower than the ion doping concentration ofthe first doped region 220. In the substrate 100 corresponding to alaterally extending region of the second doped region 230, thesemiconductor structure provided by the present invention additionallyprovides a third doped region 300, wherein the ion doping concentrationof the third doped region 300 is lower than the ion doping concentrationof the second doped region 230, and the third doped region 300 is incontact with the second doped region 230 after diffusion.

Through the structure as shown in FIG. 4 , the third doped region 300can be used together to collect near-infrared light when processingnear-infrared light, and the third doped region 300 can be used tocollect the original free photoelectrons of near-infrared light. In thisway, the effect of the parasitic light response on the image sensor canbe reduced. For the second doped region 230 of the photodiode, althoughthe second doped region 230 has been set to a deep lightly doped regionin order to more collect long wavelengths and has been laterallyexpanded to improve photoelectric efficiency, it is still not enough fordealing with near-infrared light. By making the ion doping concentrationof the third doped region 300 smaller than the ion doping concentrationof the second doped region 230, a transfer path in which photoelectronsare laterally transferred from the third doped region 300 to the seconddoped region 230 is formed, so that the photoelectrons of thenear-infrared light collected by the third doped region 300 can bestored in the first doped region 220 through the second doped region230. Thereby, it is possible to improve the light response speed of thephotodiode region and improve the accuracy of the global electronicshutter.

In the above structure, the ion doping types of the first doped region220, the second doped region 230, and the third doped region 300 are thesame, so that photoelectrons can be smoothly transferred from the thirddoped region 300 to the first doped region 220. The substrate 100 andthe pinning layer 210 have the same ion doping type, but are differentfrom the ion doping type of the first doped region 220, the second dopedregion 230 and the third doping region 300. At the same time, thepinning layer 210 is heavily doped, and the ion doping concentration ismuch higher than the ion doping concentration of the substrate 100. Inan embodiment, the first doped region 220, the second doped region 230and the third doped region 300 are all N-doped, and the substrate 100and the pinning layer 210 are both P-doped.

Further, as can be seen in the structure as shown in FIG. 4 , the thirddoped region 300 is disposed in a laterally extending region where thesecond doped region 230 extends toward the storage node. In thestructure shown in FIG. 4 , a storage node formed in the substrate 100is further included, and the storage node has a pinning layer 410 and anion doped region 420 in order from the top to the bottom in thesubstrate height direction. The third doped region 300 is formed underthe ion doped region 420, and the third doped region 300 and the iondoped region 420 are isolated from each other by the substrate 100.

Since the free electrons caused by the original near-infrared light aretransferred to the ion doped region 420 of the storage node, noise isgenerated, and since the third doped region 300 is disposed under andisolated from the ion doped region 420, it can prevent the verticaltransfer of free electrons to the storage node, greatly reducing noiseinterference.

For the ion doped region 420, since the charge originally stored in thefirst doped region 220 of the photodiode is transferred and stored inthe ion doped region 420 after the first transfer transistor TX1 isturned on, the ion doping type thereof is the same as the ion dopingtype of the first doping region 220, and the ion doping concentration isequivalent. Therefore, the ion doping concentration of the ion dopedregion 420 is greater than the ion doped concentration of the thirddoped region 300. Thereby, in order to prevent photoelectrons in thethird doped region 300 from forming a transfer channel transferred tothe ion doped region 420, the third doped region 300 needs to beimplanted deeper so as to be separated from the ion doped region 420.

The pinning layer 410 of the storage node and the substrate 100 are ofthe same doping type. Similarly, the pinning layer 410 is heavily doped,and the ion doping concentration is higher than the doping concentrationof the substrate 100. In an embodiment, the first doped region 220, thesecond doped region 230, the third doped region 300 and the ion dopedregion 420 are all N-doped, and the pinning layer 210, the pinning layer410 and the substrate 100 are all P-doped.

In the first embodiment described above, by adding an additional dopedregion at the bottom of the storage node, the concentration of thisdoping is controlled to be lower than the photodiode region, forming anelectron lateral transfer path from the bottom region of the storagenode to the bottom region of the photodiode. On the one hand, the idlearea at the bottom of the storage node can be used to additionallycollect photoelectrons generated by near-infrared light to enhance thephoto-responsive speed of the photodiode. On the other hand, theadditional doped region also reduces the probability of the freephotoelectron being transferred longitudinally to the storage node;thereby it can reduce the light response speed of the storage node areaand improve the accuracy of the global electronic shutter.

Preferably, please refer to FIG. 5 . FIG. 5 illustrates anotherembodiment of a semiconductor structure provided by the presentinvention. In the embodiment shown in FIG. 5 , its structure issubstantially the same as that of the embodiment shown in FIG. 4 . Thedifference is that, compared with the semiconductor structure shown inFIG. 4 , a fourth doped region 500 is added between the third dopedregion 300 and the ion doped region 420, and the third doped region 300and the ion doped region 420 are blocked by the fourth doped region 500.Thereby, the isolation effect between the third doped region 300 and theion doped region 420 is significantly improved.

Further, in order to function as a barrier, the ion doping type of thefourth doped region 500 is different from the third doped region 300 andthe ion doped region 420. In one embodiment, the third doped region 300and the ion doped region 420 are N-type doped, the fourth doped region500 and the substrate 100 are P-type doped. Moreover, the ion dopingconcentration of the fourth doped region 500 is higher than the dopingconcentration of the substrate 100, which effectively blocks thetransfer of photoelectrons from the third doped region 300 to the iondoped region 420.

By adding the fourth doped region 500 between the third doped region 300and the ion doped region 420, the third doped region 300 can be made tobe separated from the ion doped region 420 without being injected toodeeply. Thereby simplifies the formation of the third doped region 300.

More preferably, please refer to FIG. 6 , which illustrates anotherembodiment of a semiconductor structure provided by the presentinvention. In the embodiment shown in FIG. 6 , the structure issubstantially the same as the embodiment shown in FIG. 5 . Thedifference is that, compared with the semiconductor structure shown inFIG. 5 , the fourth doped region 500 further includes an extendingportion 510 extending laterally toward the photodiode, and the extendingportion 510 further extends upward in the substrate height direction.

By providing the extending portion 510 of the barrier layer, it ispossible to protect the ion implantation region of the storage node frombelow and near the side of the photodiode in the photoelectroncollection phase, preventing noise of free near-infrared light fromentering the ion implantation region of the storage node.

Moreover, by providing the extending portion 510 of the barrier layer,accurate transfer of photoelectrons can also be achieved duringphotoelectron transfer. As described above, the charge stored in thefirst doped region 220 of the photodiode is transferred to the ion dopedregion 420 of the storage node after the first transfer transistor TX1is turned on. In this transfer process, it is desirable to enablephotoelectrons to be transferred from the photodiode to the storage nodevia the surface of the substrate 100 as much as possible, therebyensuring the accuracy of transfer, reducing errors, and reducing noise.Therefore, by additionally providing a barrier layer to extend towardthe photodiode region, and to extend toward the surface of the substrate100, a potential barrier can be formed, so that the photoelectrons aretransferred as much as possible via the surface of the substrate 100during transfer, thereby ensuring the accuracy of the transfer andimproving the accuracy of the global shutter image sensor.

Thus far, the semiconductor structure provided by the present inventionfor forming a CMOS image sensor has been described. According to thesemiconductor structure provided by the present invention, it ispossible to effectively collect near-infrared light, reduce theparasitic light effect caused by near-infrared light scattering, enhancethe optical response speed of the image sensor, and improve the abilityof the global shutter image sensor to process near-infrared light. Morepreferably, the semiconductor structure provided by the invention canalso ensure that the storage node is not affected by the freephotoelectron noise, and at the same time, can ensure the accuratetransfer of the charge stored in the photodiode light during thetransfer, thereby improving the accuracy of the transfer and improvingthe accuracy of the global shutter image sensor.

Please referring to FIGS. 7A and 7B, FIG. 7A shows an energy potentialdiagram along the AA′ direction in an embodiment of the semiconductorstructure shown in FIG. 6 . FIG. 7B shows an energy potential diagramalong the BB′ direction in an embodiment of the semiconductor structureshown in FIG. 6 .

In FIG. 7A, the ordinate indicates the potential with respect toelectrons, and the abscissa indicates the distance coordinate of theA-A′ direction. As can be seen from FIG. 7A, the newly added fourthdoped region 500 acts as a barrier to block the effects of externalphotoelectrons.

In FIG. 7B, the ordinate indicates the potential with respect toelectrons, and the abscissa indicates the distance coordinate in theB-B′ direction. As can be seen from FIG. 7B, the newly added third dopedregion 300 acts as an additional collection layer to additionallycollect near-infrared photoelectrons and the additionally collectednear-infrared photoelectrons can be transferred to the photodiode regionstorage.

A person skilled in the art should know that the CMOS image sensor mayfurther include a global shutter GS, a second transfer transistor TX2, afloating diffusion point FD, a selection transistor RS, a resettransistor RST and the like to complete a complete processing operation,and details are not described herein again.

The present invention also provides a manufacturing method ofmanufacturing the semiconductor structure described above. Specifically,please refer to FIG. 8 , which shows a simplified flow chart of themanufacturing method provided by the present invention.

The manufacturing method provided by the present invention includes atleast step 801: providing a substrate 100; and step 802: forming asecond doped region 230, a first doped region 220 and a pinning layer210 sequentially from bottom to top in a height direction of thesubstrate in the substrate 100 to form a photodiode of the CMOS imagesensor; and step 803: forming a third doped region 300 in the substrate100 corresponding to a laterally extending region of the second dopedregion 230. The ion doping concentration of the first doped region 220is greater than the ion doping concentration of the second doped region230, and the ion doping concentration of the second doped region 230 isgreater than the ion doping concentration of the third doped region 300such that the formed third doped region 300 is in contact with thesecond doped region 230 after diffusion.

More specifically, the first doped region 220, the second doped region230 and the third doped region 300 are all of the same doping type. Inone embodiment, the doping type is N-type. The substrate 100 and thepinning layer 210 are of the same doping type, but different from thedoping types of the first doped region 220, the second doped region 230and the third doping region 300. In an embodiment, the doping type ofthe substrate 100 and the pinning layer 210 is P-type, and the iondoping concentration of the pinning layer 210 is greater than the iondoping concentration of the substrate 100.

In one embodiment, the above manufacturing method further includes:sequentially forming an ion doped region 420 and a pinning layer 410 ina substrate 100 from bottom to top in a substrate height direction toform a storage node of the CMOS image sensor; and a storage node isformed over the third doped region 300, and the third doped region 300is isolated from the ion doped region 420 of the storage node.

Specifically, the third doped region 300 and the ion doped region 420 ofthe storage node are both of the same doping type, and the ion dopingconcentration of the ion doped region 420 of the storage node is greaterthan the ion doping concentration of the third doped region 300. In anembodiment, the doping type is N-type.

More preferably, the manufacturing method provided by the presentinvention further includes forming a fourth doped region 500 between thethird doped region 300 and the ion doped region 420 of the storage node,and the third doped region 300 is isolated from the ion doped region 420of the storage node by the fourth doped region 500.

The fourth doped region 500 and the substrate 100 are both of the samedoping type, but different from the doping type of the third dopedregion 300 and the ion doped region 420 of the storage node, and the iondoping concentration of the fourth doped region 500 is greater than theion doping concentration of the substrate 100. In an embodiment, thedoping type of the substrate 100 and the fourth doped region 500 isP-type.

Still further, forming the fourth doped region 500 further includesforming an extension portion 510 extending laterally toward thephotodiode direction, and forming the extension portion 510 furtherincludes extending the extension portion 510 upward in the substrateheight direction.

It should be noted that the N-type doping referred to in the presentinvention may have a dopant such as arsenic (As), phosphorus (P), othergroup V elements or a combination of the foregoing. The P-type dopingreferred to in the present invention may have a dopant such as boron (B)or other group III element.

Those skilled in the art will appreciate that the manufacturing methodprovided by the present invention only additionally increases theformation step of the ion implantation region and is compatible with thecurrent existing process flow. And the step of ion implantation can beachieved by existing or future techniques, and is not limited thereto.

Moreover, the semiconductor structure for forming a CMOS image sensormanufactured according to the manufacturing method provided by thepresent invention can effectively collect near-infrared light, reducethe parasitic light effect caused by near-infrared light scattering,enhance the optical response speed of the image sensor, and improve theability of the global shutter image sensor to process near-infraredlight. More preferably, the semiconductor structure provided by theinvention can also ensure that the storage node is not affected by thefree photoelectron noise, and at the same time, can ensure the accuratetransfer of the charge stored in the photodiode light during thetransfer, therefore improving the transfer accuracy, and improving theaccuracy of the global shutter image sensor.

Heretofore, embodiments of the semiconductor structure and the method ofmanufacturing the same provided by the present invention have beendescribed. Although the present disclosure has been described withrespect to certain exemplary embodiments, it will be apparent thatvarious modifications and changes may be made to these embodimentswithout departing from the more general spirit and scope of thedisclosure. Accordingly, the specification and the accompanying drawingsare to be regarded in an illustrative rather than a restrictive sense.

It is to be understood that this description is not intended to explainor limit the scope or meaning of the claims. In addition, in thedetailed description above, it can be seen that various features arecombined together in a single embodiment for the purpose of simplifyingthe disclosure. The method of the present disclosure should not beinterpreted as reflecting the intention that the claimed embodimentsrequire more features than those expressly listed in each claim. Rather,as reflected by the appended claims, an inventive subject matter lies inbeing less than all features of a single disclosed embodiment.Therefore, the appended claims are hereby incorporated into the detaileddescription, with each claim standing on its own as a separateembodiment.

One embodiment or embodiments mentioned in this description is/areintended to be, combined with a particular feature, structure, orcharacteristic described in the embodiment, included in at least oneembodiment of a circuit or method. The appearances of phrases in variousplaces in the specification are not necessarily all referring to a sameembodiment.

The invention claimed is:
 1. A semiconductor structure for forming aCMOS image sensor, the semiconductor structure comprising at least aphotodiode formed in a substrate for collecting photoelectrons, whereinthe photodiode has a pinning layer, a first doped region, and a seconddoped region in order from top to bottom in a height direction of thesubstrate; and the semiconductor structure further includes a thirddoped region, wherein the third doped region is located in the substratecorresponding to a laterally extending region of the second dopedregion; wherein the ion doping concentration of the first doped regionis greater than the ion doping concentration of the second doped region,and the ion doping concentration of the second doped region is greaterthan the ion doping concentration of the third doped region, the thirddoped region is in contact with the second doped region after diffusion,wherein the semiconductor structure further comprises a storage nodeformed in the substrate, and the third doped region is formed below thestorage node, and wherein the semiconductor structure further comprisesa fourth doped region, and the third doped region is isolated from thestorage node by the fourth doped region.
 2. The semiconductor structureof claim 1, wherein the first doped region, the second doped region, andthe third doped region are all of a first ion doping type.
 3. Thesemiconductor structure of claim 2, wherein the substrate and thepinning layer are both of a second ion doping type, and the second iondoping type is different from the first ion doping type, the ion dopingconcentration of the pinned layer is greater than the ion dopingconcentration of the substrate.
 4. The semiconductor structure of claim1, wherein the storage node includes a pinning layer and an ion dopedregion in order from top to bottom in the height direction of thesubstrate, and the third doped region and the ion doped region of thestorage node are isolated from each other.
 5. The semiconductorstructure of claim 4, wherein the third doped region and the ion dopedregion of the storage node are both of a first ion doping type, and theion doping concentration of the ion doped region of the storage node isgreater than the ion doping concentration of the third doped region. 6.The semiconductor structure of claim 5, wherein the third doped regionis isolated from the ion doped region of the storage node by the fourthdoped region.
 7. The semiconductor structure of claim 1, wherein thesubstrate and the fourth doped region are both of a second ion dopingtype, the second ion doping type is different from the first ion dopingtype, and the ion doping concentration of the fourth doped region isgreater than the ion doping concentration of the substrate.
 8. Thesemiconductor structure of claim 6, wherein the fourth doped regionfurther comprises an extension extending laterally toward thephotodiode, and the extension further extends upward in the heightdirection of the substrate.
 9. A semiconductor structure for forming aCMOS image sensor, the semiconductor structure comprising at least aphotodiode formed in a substrate for collecting photoelectrons, whereinthe photodiode has a pinning layer, a first doped region, and a seconddoped region in order from top to bottom in a height direction of thesubstrate; and the semiconductor structure further includes a thirddoped region, wherein the third doped region is located in the substratecorresponding to a laterally extending region of the second dopedregion; wherein the ion doping concentration of the first doped regionis greater than the ion doping concentration of the second doped region,and the ion doping concentration of the second doped region is greaterthan the ion doping concentration of the third doped region, the thirddoped region is in contact with the second doped region after diffusion,wherein the first doped region, the second doped region, and the thirddoped region are all of a first ion doping type, and wherein thesemiconductor structure further comprises a storage node formed in thesubstrate, and the third doped region is formed below the storage node.10. The semiconductor structure of claim 9, wherein the substrate andthe pinning layer are both of a second ion doping type, and the secondion doping type is different from the first ion doping type, the iondoping concentration of the pinned layer is greater than the ion dopingconcentration of the substrate.
 11. The semiconductor structure of claim9, wherein the storage node includes a pinning layer and an ion dopedregion in order from top to bottom in the height direction of thesubstrate, and the third doped region and the ion doped region of thestorage node are isolated from each other.
 12. The semiconductorstructure of claim 11, wherein the third doped region and the ion dopedregion of the storage node are both of the first ion doping type, andthe ion doping concentration of the ion doped region of the storage nodeis greater than the ion doping concentration of the third doped region.